Eric Mickelson

Marrow Transplantation from Related Donors Other Than HLA-Identical Siblings

Marrow transplantation has generally been limited to patients with a sibling who is genotypically identical for HLA. In a study of the acceptable limits of HLA incompatibility, 105 consecutive patients with hematologic cancers who received marrow grafts from haploidentical donors (study group) were compared with 728 similar patients concurrently receiving grafts from HLA genotypically identical siblings (control group). The unshared haplotypes differed variably: 12 were phenotypically but not genotypically identical for HLA-A, HLA-B, and HLA-D; 63 differed at one locus (A, B, or D); 24 at two loci; and 6 at three. A higher proportion of study patients had delayed engraftment, granulocytopenia, or graft rejection. Acute graft versus host disease occurred earlier and with greater frequency in study patients. The risk of the disease did not correlate with disparity for Class I (A or B) versus Class II (D-region) loci. Thus, incompatibility for HLA has an important effect on the course after clinical marrow transplantation. In spite of these complications, there was no statistically significant difference in the survival of the study patients and control patients who received their transplants during remission.

Effect of HLA Compatibility on Engraftment of Bone Marrow Transplants in Patients with Leukemia or Lymphoma

We analyzed the relevance of HLA compatibility to sustained marrow engraftment in 269 patients with hematologic neoplasms who underwent bone marrow transplantations. Each patient received marrow from a family member who shared one HLA haplotype with the patient but differed to a variable degree for the HLA-A, B, and D antigens of the haplotype not shared. These 269 patients were compared with 930 patients who received marrow from siblings with identical HLA genotypes. All patients were treated with cyclophosphamide and total-body irradiation followed by the infusion of unmodified donor marrow cells. The rate of graft failure was 12.3 percent among the recipients of marrow from a donor with only one identical haplotype, as compared with 2.0 percent among recipients of marrow from a sibling with the same HLA genotype (both haplotypes inherited from the same parents) (P less than 0.0001). The incidence of graft failure correlated with the degree of donor HLA incompatibility. Graft failure occurred in 3 of 43 transplants (7 percent) from donors who were phenotypically HLA-matched with their recipient (haplotypes similar, but not inherited from the same parents), in 11 of 121 donors (9 percent) incompatible for one HLA locus, in 18 of 86 (21 percent) incompatible for two loci, and in 1 of 19 (5 percent) incompatible for three loci (P = 0.028). In a multivariate binary logistic regression analysis, independent risk factors associated with graft failure were donor incompatibility for HLA-B and D (relative risk = 2.1; 95 percent confidence interval, 1.7 to 2.5; P = 0.0004) and a positive crossmatch for anti-donor lymphocytotoxic antibody (relative risk = 2.3; 95 percent confidence interval, 1.8 to 2.8; P = 0.0038). Residual host lymphocytes were detected in 11 of 14 patients with graft failure, suggesting that the mechanism for graft failure could be host-mediated immune rejection. We conclude that donor HLA incompatibility and prior alloimmunization are significant risk factors for graft failure, and that a more effective immunosuppressive regimen than those currently used is needed for consistent achievement of sustained engraftment of marrow transplanted from donors who are not HLA-identical siblings.

Killer Ig-Like Receptor Haplotype Analysis by Gene Content: Evidence for Genomic Diversity with a Minimum of Six Basic Framework Haplotypes, Each with Multiple Subsets

Killer Ig-like receptor (KIR) genes constitute a multigene family whose genomic diversity is achieved through differences in gene content and allelic polymorphism. KIR haplotypes containing a single activating KIR gene (A-haplotypes), and KIR haplotypes with multiple activating receptor genes (B-haplotypes) have been described. We report the evaluation of KIR gene content in extended families, sibling pairs, and an unrelated Caucasian panel through identification of the presence or absence of 14 KIR genes and 2 pseudogenes. Haplotype definition included subtyping for the expressed and nonexpressed KIR2DL5 variants, for two alleles of pseudogene 3DP1, and for two alleles of 2DS4, including a novel 2DS4 allele, KIR1D. KIR1D appears functionally homologous to the rhesus monkey KIR1D and likely arose as a consequence of a 22 nucleotide deletion in the coding sequence of 2DS4, leading to disruption of Ig-domain 2D and a premature termination codon following the first amino acid in the putative transmembrane domain. Our investigations identified 11 haplotypes within 12 families. From 49 sibling pairs and 17 consanguineous DNA samples, an additional 12 haplotypes were predicted. Our studies support a model for KIR haplotype diversity based on six basic gene compositions. We suggest that the centromeric half of the KIR genomic region is comprised of three major combinations, while the telomeric half can assume a short form with either 2DS4 or KIR1D or a long form with multiple combinations of several stimulatory KIR genes. Additional rare haplotypes can be identified, and may have arisen by gene duplication, intergenic recombination, or deletions.

Marrow transplantation from HLA-matched unrelated donors for treatment of hematologic malignancies

Less than 40% of the patients who could benefit from marrow transplantation have an HLA-matched relative who can serve as a donor. For this reason, several centers have explored marrow transplantation from other categories of donors. This retrospective study analyzes the results of marrow transplantation for 52 patients receiving grafts from HLA-A,B,DR,Dw-phenotypically matched, MLC-compatible, unrelated volunteer donors compared to a disease, disease-stage, and age-matched cohort of 104 patients transplanted from HLA-genotypically identical sibling donors. The patients transplanted from unrelated donors had an increased incidence of grade II-IV acute graft-versus-host disease compared to patients transplanted from related donors (79% vs. 36%, P much less than 0.001). However, the probability of relapse-free survival appears similar in the two groups (P = 0.39 over all, with estimates of 41% vs. 46% at 1 year). We conclude from this preliminary data that marrow transplantation from HLA-matched unrelated donors should be considered in most, if not all, circumstances where transplantation from an HLA-matched sibling would be indicated if such a donor were available.

Factors associated with graft rejection after HLA-identical marrow transplantation for aplastic anaemia

Summary. One hundred and seventy‐five consecutive patients with severe aplastic anaemia were given high‐dose cyclophosphamide followed by marrow grafts from healthy, HLA‐identical family members, and 168 lived long enough to show engraftment. In 38 patients the graft was rejected and 29 of these died. This analysis, using a binary logistic regression model, was aimed at identifying factors that predicted marrow graft rejection. Five factors correlated with graft rejection: (1) previous blood transfusion; (2) a positive relative response in mixed leucocyte culture indicating sensitization of patient against donor; (3) a low number of marrow cells used for transplantation; (4) marrow grafts from male donors; and (5) lack of infusion of viable donor buffy coat cells in addition to the marrow for transfused patients. The findings confirm the importance of transplanting early before transfusion and indicate that the greatest possible amount of donor marrow (supplemented by stem cells/lymphoid cells derived from the peripheral blood) should be obtained.

The biological significance of HLA‐DP gene variation in haematopoietic cell transplantation

Although it has been over 25 years since HLA‐DP was mapped to the major histocompatibility complex (MHC), its biological functions remain ill‐defined. We sought to test the hypothesis that HLA‐DP functions in a manner similar to that of other class II genes by measuring the risk of clinically severe grades III–IV acute graft‐vs.‐host disease (GVHD) associated with recipient HLA‐DP disparity after haematopoietic cell transplantation. HLA‐DPB1 exon 2 was sequenced in 205 patients who underwent transplantation from HLA‐A, ‐B, ‐C, ‐DRB1 and ‐DQB1 allele‐matched unrelated donors. HLA‐DPB1 mismatched recipients experienced a significantly increased risk of acute GVHD compared with HLA‐DP‐identical transplants. Patients who were mismatched for a single HLA‐DPB1 allele had an odds ratio (OR) of 1·0 (0·5, 2·2; P = 0·99) and patients who were mismatched for two alleles had an OR of 2·2 (1·0, 4·9; P = 0·06) for developing acute GVHD. Compared with matched and single‐allele mismatched transplants, patients who were mismatched for two DPB1 alleles had an OR of 2·2 (1·2, 4·1; P = 0·01). HLA‐DP plays an important role in the alloimmune response. A threshold effect of multiple HLA‐DP disparities is evident in determining the risk of acute GVHD after haematopoietic cell transplantation from unrelated donors.

Specific HLA-DR4-associated histocompatibility molecules characterize patients with seropositive juvenile rheumatoid arthritis.

The structural and functional heterogeneity of HLA-DR4-associated specificities was investigated in patients with seropositive juvenile rheumatoid arthritis, a DR4-associated disease. Using a combination of HLA-D analysis by mixed lymphocyte culture and electrophoretic analysis of immunoprecipitated Ia molecules by two-dimensional polyacrylamide gels, we observed a surprisingly homogeneous pattern of HLA-D antigen expression. All patients expressed common structural products of the DR and DS loci, and 7/12 homozygous DR4 patients expressed a rare and subtle HLA-D heterozygous phenotype.

Ten HLA-DR4 alleles defined by sequence polymorphisms within the DRB1 first domain.

We have studied DRB1 sequence polymorphisms associated with DR4 subtypes using DR4-specific DNA amplification and sequence-specific oligonucleotide probe (SSOP) hybridization. The 5′ amplification primer was designed to hybridize with a unique sequence in the first hypervariable region (HVR) of the DRB1 second ex-on of all known DR4 alleles; the 3′ primer was designed to hybridize with an intron sequence common to all DRB1 alleles. The specificity of the amplification step was demonstrated by double-blind testing of 105 selected DNA samples. Prospective SSOP typing of DR4 alleles was performed in 104 unrelated individuals known to be DR4-positive, including 13 who were DR4-homozygous. A DRB1 subtype corresponding with the previously defined DR4-associated specificities Dw4, Dw10, Dw13.1, Dw13.2, Dw14.1, Dw14.2, Dw15, and DwKT2 could be assigned for each of the 117 DR4 haplotypes tested. In most cases, DR4-homozygous, DRB1-heterozygous individuals could be genotyped with the panel of probes. In the course of our analysis, we identified two new DR4-related alleles, DRB1*04.CB (DRB1*0410)1 and DRB1*04.EC (DRB1*, 0411)2 which were recognized by their novel hybridization patterns. The DRB1 second exon sequence of DRB1*04.CB, is identical to DRB1*0405 except at codon 86 where GTG encodes valine instead of GGT encoding glycine. DRB1*04.EC is identical to DRB1*04.CB except at codon 74 where GAG encodes glutamic acid instead of GCG encoding alanine. Our results provide further evidence that SSOP hybridization is the most effective approach available for subtyping DR4 haplotypes and identifying unrecognized variants. A similar approach should be equally informative for subtyping other DR alleles.

Marrow Grafts Between Dl-a-matched Canine Littermates

SUMMARY Three groups of recipient dogs were conditioned for transplantation by supralethal exposure to total body irradiation from dual 60Co sources and then given hemopoietic grafts from DL-A-matched littermates. Group 1 consisted of 17 dogs given marrow cells only and not treated with immunosuppressive therapy postgrafting. Group 2 was made up of 11 dogs given a combination of marrow and peripheral blood leukocytes and no postgrafting immunosuppression. Group 3 included 13 dogs given a combination of marrow and peripheral blood leukocytes and intermittent methotrexate (MTX) therapy for 102 days postgrafting. Nine of the 17 recipients in group 1 died between 30 and 230 days after grafting with graft-versus-host (GVH) disease. Eight recipients survived beyond 230 days without GVH disease. Seven of 11 recipients in group 2 died with GVH disease after 12–151 days and 4 survived beyond 200 days. One dog in group 3 died on day 61, and 12 survived beyond 200 days without evidence of GVH disease. Thus, fatal GVH disease was seen in a number of canine recipients not given postgrafting immunosuppression despite DL-A matching with their littermate donor. The addition of peripheral blood leukocytes to the marrow inoculum did not significantly change the overall survival but increased the severity of GVH disease. Therapy with intermittent MTX postgrafting significantly prolonged survival (P < 0.01) and resulted in the establishment of stable graft-host “tolerance” in most DL-A-matched recipients.

Marrow transplantation from donors other than HLA-identical siblings.

Twelve patients with acute leukemia and nine with aplastic anemia received marrow transplants from donors other than genotypically HLA-identical siblings. All donor-recipient pairs were genotypically identical for one HLA haplotype and shared antigens of the other. Of nine transplants between siblings, three were HLA-D incompatible and one HLA-A and B incompatible as a consequence of B-D recombination. One such recipient survives in good health at day 485. Three sibling pairs had parents homozygous for HLA-A and B and heterozygous for HLA-D. One rejected the transplant, one died of interstitial pneumonia, and one died of persistent leukemia. Two sibling pairs had parents homozygous for HLA-D but not for HLA-A and B. One recipient died of graft rejection on day 93, and one survives in good health at day 339. Three patients had parent donors identical for HLA-A, B, and D. One survives at day 742. Of two recipients whose parent donors were HLA-A and B compatible and D incompatible, one has minimal graft-versus-host disease (GVHD) at day 361, and one died of graft rejection at day 47. Six recipients had parent donors matched for HLA-D but not for HLA-A or B. One survives with recurrent leukemia in postchemotherapy remission at day 690, three died of graft rejection and two of GVHD. One recipient was HLA-D homozygous, received marrow from his HLA-A-mismatched, HLA-D heterozygous parent and died of graft rejection on day 47. The experience of GVHD was within the range encountered in transplants between genotypically HLA-identical siblings. The number of patients receiving transplants is much too small to permit any conclusions about the relative importance of various degrees and varieties of mismatching, but the results encourage further studies of well defined deviations from the HLA-identical sibling relationship in marrow transplantation. There is an increasing number of reports of marrow transplantation between identical twins or genotypically HLA-identical siblings as part of the therapy of aplastic anemia or hematological malignancy (1–5). We are extending our studies of marrow transplantation by performing allogeneic marrow transplants from donors other than HLA-matched siblings to evaluate the effects of precise histocompatibility differences. This paper reports our experience in this endeavor and presents the details of 21 such transplants.